JP7186811B2 - Measuring device and measuring method - Google Patents

Description

The present invention relates to a measuring device and a measuring method.

Patent Literature 1 discloses a method of measuring deformation of a large-sized structure having a length of 100 m, for example, using a plurality of optical fiber cables.

JP-A-2000-17678

In order to enable measurement with a simpler configuration, a single optical fiber can be used to measure changes in tilt amount and cross-sectional performance (neutral axis position, section modulus, etc.) accompanying deformation of the measurement target. was required.

The present invention has been made in consideration of such circumstances, and uses a single optical fiber to measure the amount of tilt and change in cross-sectional performance (neutral axis position, section modulus, etc.) accompanying deformation of the object to be measured. The purpose is to provide an apparatus or a measuring method.

In order to solve the above problems, a measuring device according to a first aspect of the present invention includes one optical fiber formed with an FBG, an optical measuring instrument connected to the optical fiber, and a measuring device in contact with the optical fiber. A first guide member having a first arcuate surface and a second guide member having a second arcuate surface in contact with the optical fiber, wherein the first guide member and the second guide member are spaced apart in one direction. The optical fiber is arranged with a space therebetween and is fixed to an object to be measured. and a second portion in contact with the arcuate surface and the second arcuate surface, wherein the second portion is arranged so as to separate from the measurement surface as it goes from the first arcuate surface to the second arcuate surface. .

According to the above aspect, a single optical fiber is used to measure the tilt amount of the measurement surface due to the deformation of the measurement object and the change in cross-sectional performance (the position of the neutral axis, the section modulus, etc.) of the measurement object. be able to. In addition, it is possible to precisely and continuously measure the deformation of the structure as the object to be measured in minute sections.

Here, the measuring device may further include a base member to which the first guide member and the second guide member are fixed, and the base member may be fixed to the measurement object.

A measuring method according to a second aspect of the present invention provides a tension-applied section to which tension is applied and a tension-free section to which no tension is applied to one optical fiber on which an FBG is formed, and Temperature calibration is performed using the measurement result of the strain amount of the optical fiber in the section, and the measurement result of the strain amount of the optical fiber in the tension application section is used to determine the deformation caused by the deformation of the measurement object. Measure the amount of inclination of the measurement surface of the object to be measured.

A measurement method according to a third aspect of the present invention is a single optical fiber having an FBG formed thereon, a first portion arranged along a measurement surface of an object to be measured, and a linear separation from the measurement surface. and a second portion arranged as above, based on the strain generated in the first portion and the strain generated in the second portion accompanying deformation of the measurement object, the measurement object Measure the distance of the neutral axis from the measurement plane.

A measurement method according to a fourth aspect of the present invention is to fix one optical fiber formed with an FBG to an object to be measured, and measure the amount of strain generated in the optical fiber due to the deformation of the object to be measured. to measure the amount of tilt of the object to be measured in a first direction and the amount of tilt in a second direction orthogonal to the first direction.

In the above measuring method, twist of the object to be measured about an axial direction perpendicular to both the first direction and the second direction may be measured using the amount of strain generated in the optical fiber.

According to the above aspect of the present invention, a measuring device or a measuring method capable of measuring changes in the amount of tilt and cross-sectional performance (position of the neutral axis, section modulus, etc.) accompanying deformation of the object to be measured using a single optical fiber. can be provided.

It is the figure which looked at the measuring device concerning a 1st embodiment from the 1st direction. FIG. 1B is a view of the measuring device of FIG. 1A viewed from a second direction; It is a schematic diagram for explaining a measuring method concerning a 1st embodiment. 2B is a schematic diagram showing a state after the measurement object of FIG. 2A is deformed; FIG. It is the figure which looked at the measuring device which concerns on 2nd Embodiment from the 1st direction. FIG. 3B is a view of the measuring device of FIG. 3A viewed from a second direction; It is the figure which looked at the measuring device concerning a 3rd embodiment from the 1st direction. FIG. 4B is a view of the measuring device of FIG. 4A viewed from a second direction; FIG. 2 is a diagram showing a first usage example of the measurement devices of the first to third embodiments; FIG. 10 is a diagram showing a second example of use of the measuring devices according to the first to third embodiments; FIG. 6B is a cross-sectional view taken along line VI-VI of FIG. 6A. FIG. 10 is a diagram showing a third usage example of the measurement devices of the first to third embodiments; 7B is a cross-sectional view taken along line VII-VII of FIG. 7A. FIG. It is the figure which looked at the measuring device concerning a 4th embodiment from the 1st direction. It is the figure which looked at the measuring device of FIG. 8 from the 2nd direction. It is a figure for demonstrating the measurement principle which concerns on 4th Embodiment. It is a figure for demonstrating the measurement principle which concerns on 4th Embodiment.

(First embodiment)
The measuring device of the first embodiment will be described below with reference to the drawings.
As shown in FIG. 1, the measuring device 1 includes a mounting unit 10 and an optical measuring device 20. As shown in FIG. The mounting unit 10 includes a sheet material 11 , a base member 12 , a first guide member 13 , a second guide member 14 and one optical fiber 15 . The mounting unit 10 is fixed to the surface of the measurement object T (measurement surface t1). An FBG (Fiber Bragg Grating) is formed in the optical fiber 15 . The optical measuring instrument 20 is configured to measure strain at each part of the optical fiber 15 by emitting measurement light to the optical fiber 15 and analyzing reflected light reflected by the FBG. Specifically, the optical measuring device 20 measures the distortion of each part of the optical fiber 15 by OFDR (Optical Frequency Domain Reflectometry). The optical measuring device 20 may or may not be fixed to the object T to be measured. Since the optical measuring instrument 20 is a precision instrument, it is preferable to arrange the optical measuring instrument 20 on the ground apart from the measuring object T, especially when the measuring object T is installed in the ground or in the sea.

A measurement target T is an arbitrary structure or the like. Specifically, steel pipe piles, steel pipe sheet piles, steel sheet piles (U type, Z type, hat type, straight type, etc.), H type steel, PC walls, PC piles, bridge members, building members (columns, beams, walls), storage facilities, walls and ceilings of underground spaces and tunnels. However, the measuring apparatus 1 and the measuring method of the present embodiment may be applied to the measurement object T other than the above.

(direction definition)
In this embodiment, an XYZ orthogonal coordinate system is set to describe the positional relationship of each component. The axial direction of the optical fiber 15 is referred to as the axial direction Z and is represented by the Z axis in the drawings. In the axial direction Z, the side of the optical measuring device 20 is indicated as the -Z side, and the opposite side is indicated as the +Z side. One direction orthogonal to the axial direction Z is referred to as a first direction X and is represented by the X axis in the drawings. A direction perpendicular to both the axial direction Z and the first direction X is referred to as a second direction Y, represented by the Y-axis in the drawings. The first direction X is a direction perpendicular to the measurement plane t1 of the measurement object T before deformation, and the second direction Y is a direction parallel to the measurement plane t1 before deformation. In the first direction X, the side of the mounting unit 10 viewed from the measurement target T is indicated as the +X side, and the opposite side is indicated as the -X side. In the second direction Y, one side is indicated as the +Y side and the other side is indicated as the -Y side.
According to the measurement apparatus 1 and the measurement method of the first embodiment, the amount of inclination of the measurement object T in the first direction X and the change in cross-sectional performance (the position of the neutral axis, the section modulus, etc.) of the measurement object T are measured. It is possible.

The sheet material 11 is used for facilitating attachment of other constituent members of the attachment unit 10 to the measurement object T. As shown in FIG. As the sheet material 11, a material that can be fixed to the measurement surface t1 of the measurement object T and that deforms following the deformation of the measurement surface t1 is suitable. The sheet material 11 is, for example, a metal (SUS) sheet having a thickness of 0.01 to 0.3 mm. Note that the sheet material 11 may be omitted, and the base member 12 may be directly attached to the measurement object T, for example.

The base member 12 fixes the distance between the first guide member 13 and the second guide member 14, and displaces the first guide member 13 and the second guide member 14 following the deformation of the measurement surface t1. Used. As the base member 12, a material capable of fixing the first guide member 13 and the second guide member 14 and deforming following the deformation of the measurement surface t1 is suitable. In the example of FIGS. 1A and 1B, the base member 12 is two rails extending along the Z-axis direction. Each rail is, for example, a metal (SUS) rectangular bar having a width and thickness of 0.3 to 0.5 mm. The two rails are spaced apart in the second direction Y, and a portion of the optical fiber 15 is positioned between the rails. The shape of the base member 12 can be changed as appropriate, and for example, two rails may be connected and integrated.

Each of the first guide member 13 and the second guide member 14 has arcuate surfaces 13a and 14a at least partially, and the optical fiber 15 abuts on the arcuate surfaces 13a and 14a. The first guide member 13 and the second guide member 14 of the present embodiment have a columnar shape with a center axis along the second direction Y, and outer peripheral surfaces thereof are the aforementioned circular arc surfaces 13a and 14a. The shapes of the first guide member 13 and the second guide member 14 can be changed as appropriate, and may be, for example, a semi-cylindrical shape or a cylindrical shape.

The first guide member 13 and the second guide member 14 are spaced apart in the axial direction Z. As shown in FIG. The first guide member 13 is positioned on the -Z side, and the second guide member 14 is positioned on the +Z side. As shown in FIG. 1B, in this embodiment, an arbitrary section between the optical measuring device 20 and the first guide member 13 in the axial direction Z is called a Z-axis measurement section Sz. 2 guide member 14 is called an X-axis measurement section Sx. A portion of the optical fiber 15 located in the Z-axis measurement section Sz is called a first portion P1, and a portion located in the X-axis measurement section Sx is called a second portion P2. A predetermined tension is applied to the optical fiber 15 at least at the first portion P1 and the second portion P2. In other words, the Z-axis measurement section Sz and the X-axis measurement section Sx are sections in which tension is applied to the optical fiber 15 (hereinafter referred to as "tension application sections").

As shown in FIG. 1B, the first portion P1 of the optical fiber 15 located in the Z-axis measurement section Sz is linearly arranged along the measurement plane t1. The optical fiber 15 is passed through the -X side of the first guide member 13, that is, between the first guide member 13 and the measurement surface t1. Also, the optical fiber 15 is passed through the unit side (+X side) of the second guide member 14 . Since a predetermined tension is applied to the optical fiber 15 , the optical fiber 15 contacts the arc surface 13 a of the first guide member 13 and the arc surface 14 a of the second guide member 14 . Also, the optical fiber 15 is linearly stretched between the first guide member 13 and the second guide member 14 due to the tension.

2A and 2B are schematic diagrams for explaining the measurement principle of the measurement device 1 of this embodiment. FIG. 2B shows a state in which a load in the first direction X (a bending moment M about an axis extending in the second direction Y) acts on the measurement object T, and bending deformation occurs in the measurement object T. there is In FIGS. 2A and 2B, the first portion P1 and the second portion P2 of the optical fiber 15 are overlapped for convenience of explanation. Further, since the sheet material 11 and the base member 12 can be substantially ignored when considering the amount of elongation (amount of strain) of the optical fiber 15 due to the deformation of the measurement object T, they are not shown in FIGS. 2A and 2B. omitted. It should be noted that the measurement object T will be described as one that undergoes uniform and continuous deformation at least in the Z-axis measurement section Sz and the X-axis measurement section Sx.

Definitions of symbols shown in FIGS. 2A, 2B, etc. and used in the following description are as follows.
A0: The point closest to the measurement surface t1 on the arc surface 13a of the first guide member 13 B0: The point farthest from the measurement surface t1 on the arc surface 13a of the first guide member 13 A1: The arc surface of the second guide member 14 Point B1 of 14a closest to measurement surface t1: Point A'1 of arc surface 14a of second guide member 14 that is farthest from measurement surface t1: Position B of point A1 after deformation relative to point A0 '1: the position of the point B1 after relative displacement with respect to the point B0 after deformation B'1: the farthest point from the measurement surface t1 on the arc surface 14a of the second guide member 14 Laz: the point A0 before deformation occurs Distance L'az between point A1: arc length L''az between point A0 and point A'1 along measurement plane t1 after deformation: point A0 and point A'1 after deformation Linear length Lax between: Length of the second portion P2 (linear length between points A0-B1)
L'ax: Length of the second portion P2 after deformation (straight line length between points A0-B'1)
Lch: Distance between the neutral axis of the measurement object T before deformation and the measurement plane t1 L'ch: Distance between the neutral axis of the measurement object T after deformation and the measurement plane t1 ∠θa: Second portion Angle ∠θ′a formed by P2 with respect to measurement surface t1: Size of angle _∠θA0 formed by second portion P2 with respect to measurement surface t1 after deformation : ∠(B0-A0-A1) Magnitude _∠θ'A0 : Magnitude of the angle formed by the normal to the measurement plane t1 at the point A'0 and the normal to the measurement plane t1 before deformation ∠θ'A1: The measurement plane _t1 at the point A'1 The angles _∠θ′A0 and _∠θ′A1 formed by the normal to the normal to the measurement surface t1 before deformation are determined by the deformation of the measurement object T and the placement of the guide members 13 and 14. It shows the amount of tilt of the measurement target part T caused at the position.

As described above, since tension is applied to the optical fiber 15, the −Z side end of the second portion P2 of the optical fiber 15 is in contact with the point A0, and the +Z side end is in contact with the point B1. Become.
A measurement method for measuring the magnitudes of _∠θ'A0 and _∠θ'A1 using the above parameters will be described.

Comparing FIG. 2A and FIG. 2B, in FIG. 2B, due to the deformation of the measurement object T, the first portion P1 and the second portion P2 of the optical fiber 15 are distorted (elongated). The strain produced in the first portion P1 is denoted by εz, and the strain produced in the second portion P2 is denoted by εx. The values of εz and εx can be obtained by the optical measurement device 20 performing OFDR analysis. Since the values of Laz and Lax are based on the design of the measuring device 1, they are known. The value of L'az can be converted from the value of εz. The value of L″az can be converted from εx. Further, there is a relationship of L″az=R×sin(∠θ′ _A1 /2)×2. The distance between points A0 and B0 (that is, the diameter of the first guide member 13) is D1, the point where the surface of the second portion P2 of the optical fiber 15 contacts the surface 13a of the guide member 13 is 13a0, and the guide member 13 Let ∠θb be the angle between the straight line connecting the center of and the point 13a0 and the vertical direction (straight lines A0 to B0). Similarly, if the point where the surface of the second portion P2 of the optical fiber 15 contacts the surface 14a of the guide member 14 is 14b1, the angle is ∠θb. Also, if the diameter of the optical fiber 15 is Df and D'1=D1+Df, ∠θb=asin((D'1)/Laz). Also, if the point where the extension of the straight line (13a1-14b1) intersects the extension of the straight line (A1-B1) is Bf1, and the target point (intersection on the A1 side) is Af1, then the straight line (Af1-Bf1) The length is Laz×tan(∠θb)=D'i. The values of ∠θb and D'i can be calculated by trigonometric functions based on Laz and D1. Also, if the diameter of the optical fiber 15 is Df and D'1=D1+Df, then the value of _∠θ'A0 is the angle included in the triangle based on L''az, D'i, L'ax, and L''az. It can be calculated from the theorem.

Furthermore, the following formula (1) is established from the geometrical relationship.
_∠θ'A0 = _∠θA0 - _∠θ'A1 ÷ 2 (1)
By transforming the formula (1), the formula (1)' is obtained.
_∠θ'A1 =(π/2- _∠θ'A0 )×2 (1)'

Here, since ∠θ′ _A1 is calculated from L″az, equation (1)′ becomes a cyclic calculation. ' Adopt a method of calculating the value of _A1 and correcting the error after the fact. In addition, as a theoretical error, there is a phenomenon that "as εz increases, a slight difference occurs between the extending direction of the optical fiber 15 and the direction from the point A0 to the point B1". Since these produce errors of the same degree, the total theoretical error is corrected by approximating it to an exponential function of _Δ∠θ'A1 =G*εz^ ² at the final stage of the calculation (Δ∠θ'A1 is _∠θ ' _A1 change amount, G is a constant that changes with the neutral axis depth). According to such a method, the theoretical error can be made negligible.
From the above, the values of ∠θ′ _A0 and ∠θ′ _A1 (that is, the tilt amount of the measurement surface t1 due to deformation ) can be calculated.

Also, if the radius of curvature of the neutral axis of the measurement object T after deformation is R, then R=L'az/ _∠θ'A1 is established. As described above, both L'az and _∠θ'A1 are computable values, so the value of R is also computable. Since it is known that R=L'ch÷εz, the magnitude of L'ch can also be calculated.
From the above, the value of L'ch (that is, the sectional performance after deformation of the measurement object T (the position of the neutral axis and the change in section modulus, etc.) can be calculated.

The optical fiber 15 expands and contracts due to changes in temperature in addition to deformation of the object T to be measured. Therefore, the measurement result of the strain amount of the optical fiber 15 includes a component caused by the deformation of the measurement object T and a component caused by the temperature change. In order to measure the tilt amount of the object T to be measured with higher accuracy, it is preferable to remove the component caused by the temperature change from the measurement result of the optical measuring device 20 (that is, perform temperature calibration).

Therefore, in the present embodiment, in addition to the tension application section described above, a section in which no tension is applied to the optical fiber 15 (hereinafter referred to as a "non-tension section") is provided. A tension-free section can be provided at any portion of the optical fiber 15 . Since the strain amount of the optical fiber 15 in the non-tension section is caused by temperature change, temperature calibration may be performed using the strain amount.

As described above, the measurement apparatus 1 of this embodiment includes one optical fiber 15 formed with an FBG, the optical measuring device 20 connected to the optical fiber 15, and the first arcuate surface in contact with the optical fiber 15. 13a and a second guide member 14 having a second arcuate surface 14a in contact with the optical fiber 15. The first guide member 13 and the second guide member 14 are arranged in one direction (axial direction). Z) are spaced apart and fixed to the measurement object T, and the optical fiber 15 is arranged along the measurement plane t1 of the measurement object T and along the one direction. and a second portion P2 whose both ends are in contact with the first arcuate surface 13a and the second arcuate surface 14a. It is arranged away from t1.

With the configuration as described above, it is possible to measure the tilt amount of the measurement surface t1 accompanying the deformation of the measurement object T, the position of the neutral axis of the measurement object T, and the like using one optical fiber 15 . And according to the said structure, it becomes possible to measure the deformation|transformation of the structure as the measurement object T precisely and continuously in a fine area.

The measuring device 1 further includes a base member 12 to which the first guide member 13 and the second guide member 14 are fixed, and the base member 12 is fixed to the measurement object T. As shown in FIG. Thereby, the configuration for attaching the optical fiber 15 to the measurement object T can be unitized. Therefore, attachment of the optical fiber 15 to the measurement object T becomes easy.

Further, in the measurement method of the present embodiment, the one optical fiber 15 on which the FBG is formed is provided with a tension application section to which tension is applied and a non-tension section to which no tension is applied, and light in the non-tension section Temperature calibration is performed using the measurement result of the strain amount of the fiber 15, and the measurement result of the strain amount of the optical fiber 15 in the tension application section is used to measure the deformation of the measurement object T. is measured. This makes it possible to measure the tilt amount with higher accuracy.

In addition, the measurement method of this embodiment includes the first portion P1 arranged along the measurement surface t1 of the measurement object T and the and a second portion P2 arranged apart from each other, and measurement is performed based on the strain εz generated in the first portion P1 and the strain εx generated in the second portion P2 accompanying deformation of the measurement object T. The distance of the neutral axis of the object T from the measurement plane t1 is measured. With such a measurement method, it becomes possible to measure, using a single optical fiber 15, the change in the position of the neutral axis of the structure after installation, which has been difficult to measure conventionally.

(Second embodiment)
Next, a second embodiment according to the present invention will be described, but the basic configuration is the same as that of the first embodiment. For this reason, the same reference numerals are assigned to the same configurations, the description thereof is omitted, and only the points of difference will be described.

In the first embodiment, the tilt amount (values of _∠θ'A0 and _∠θ'A1 ) of the measurement object T when the load in the first direction X acts on the measurement object T is measured. In addition to this, in the present embodiment, the tilt amount of the measurement object T when the load in the second direction Y acts on the measurement object T is measured.

As shown in FIGS. 3A and 3B, in this embodiment, the third guide member 16 and the fourth guide member 17 are arranged on the +Z side of the second guide member 14 . The third guide member 16 and the fourth guide member 17 have the same configuration as the first guide member 13 and the second guide member 14, except that they have a cylindrical shape with the center axis along the first direction X. As shown in FIG. In this embodiment, the section between the third guide member 16 and the fourth guide member 17 is called a Y-axis measurement section Sy. The Y-axis measurement section Sy is also a tension application section.

The optical fiber 15 is passed through the +Y side of the third guide member 16 and the -Y side of the fourth guide member 17 . The optical fiber 15 is in contact with the arc surface 16 a of the third guide member 16 and the arc surface 17 a of the fourth guide member 17 . Accordingly, the optical fiber 15 extends linearly from one side in the second direction Y toward the other side in the Y-axis measurement section Sy. In the Y-axis measurement section Sy, the optical fiber 15 is located at a position apart from the measurement surface t1 on the +X side by a certain distance.

In this embodiment, the strain generated in the optical fiber 15 in the Y-axis measurement section Sy due to the deformation due to the load acting on the measurement object T in the second direction Y is referred to as εy. The value of εy can also be obtained by OFDR using the optical measuring instrument 20 . Based on the value of εy, by using the same method as in the first embodiment, the tilt amount of the measurement object T when the load in the second direction Y acts on the measurement object T can be measured. Furthermore, the position of the neutral axis of the measurement object T in the second direction Y can also be measured in the same manner as in the first embodiment.

As described above, according to the measurement method of the present embodiment, one optical fiber 15 having an FBG formed thereon is fixed to the measurement object T, and the optical fiber 15 is Using εx, εy, and εz, which are strain amounts generated in the Become.

(Third embodiment)
Next, a third embodiment according to the present invention will be described, but the basic configuration is the same as that of the second embodiment. For this reason, the same reference numerals are assigned to the same configurations, the description thereof is omitted, and only the points of difference will be described.

In the second embodiment, the tilt amount of the measurement object T when the loads in the first direction X and the second direction Y act on the measurement object T are measured. In addition to this, in the present embodiment, the amount of torsion around the axial direction Z that occurs in the measurement object T is measured.

As shown in FIGS. 4A and 4B, in this embodiment, a fifth guide member 18, a sixth guide member 19, a seventh guide member 21, and an eighth guide member 22 are provided on the +Z side of the third guide member 16. are placed. The configurations of the fifth guide member 18 and the sixth guide member 19 are the same as the configurations of the first guide member 13 and the second guide member 14 . The configurations of the seventh guide member 21 and the eighth guide member 22 are the same as the configurations of the third guide member 16 and the fourth guide member 17 . In this embodiment, the section between the fifth guide member 18 and the sixth guide member 19 is called a secondary X-axis measurement section Sx'. Also, the section between the seventh guide member 21 and the eighth guide member 22 is called a secondary Y-axis measurement section Sy'. An arbitrary section on the +Z side of the eighth guide member 22 is called a secondary Z-axis measurement section Sz'. The secondary X-axis measurement section Sx', the secondary Y-axis measurement section Sy', and the secondary Z-axis measurement section Sz' are also tension application sections. It should be noted that the object to be measured T is assumed to undergo uniform and continuous deformation in both the amount of tilt and the amount of twist at least in these tension application sections.

The length in the axial direction Z of the secondary Y-axis measurement section Sy' must not be the same as the length in the axial direction Z of the Y-axis measurement section Sy (preferably an integer multiple). The number of secondary X-axis measurement sections Sx', secondary Y-axis measurement sections Sy', and secondary Z-axis measurement sections Sz' may be plural (n locations). n is an integer of 1 or more. Of the n points, the position where the target secondary X-axis measurement section Sx', secondary Y-axis measurement section Sy', and secondary Z-axis measurement section Sz' are provided is represented as i, and the X-axis measurement section Sx and the Y-axis measurement When the position where section Sy and Z-axis measurement section Sz are provided is expressed as i=1, in this embodiment, the relative tilt change between (i) to (i+1) is calculated. It is assumed that there is a change in the amount of tilt in both the first direction X and the second direction Y between (i) and (i+1) and that twist occurs. Based on the measurement results of the X-axis measurement section Sx and the Y-axis measurement section Sy, or the measurement results of the secondary X-axis measurement section Sx' and the secondary Y-axis measurement section Sy', the combined tilt angle βz on the XY projection plane is obtained. By comparing the combined tilt angle βz at the position (i) and the position (i+1), the amount of change (Δβz) in the combined tilt angle can be detected. This Δβz is the amount of twist generated between (i) and (i+1).

As described above, according to the present embodiment, the amount of strain generated in the optical fiber 15 is used to detect the twist of the measurement object T around the axial direction Z orthogonal to both the first direction X and the second direction Y. It is possible to measure

Next, usage examples of the measuring device 1 of the first to third embodiments will be described.
As shown in FIG. 5, a plurality of attachment units 10 may be attached to one columnar measurement target T, and a common optical fiber 15 may be fixed to these attachment units 10 . In this case, one optical measuring device 20 and one optical fiber 15 can be used to measure the tilt amount, neutral axis, and twist of the measurement object T at the position of each mounting unit 10 .

Also, as shown in FIGS. 6A and 6B, a plurality of mounting units 10 may be attached to the inner peripheral surface of one cylindrical measurement object T along the longitudinal direction of the cylinder. This measurement object T is specifically a steel pipe pile or the like, and the measurement surface t1 is the inner peripheral surface of the steel pipe pile or the like. In this case, the axial direction Z of the optical fiber 15 and the longitudinal direction of the steel pipe pile match. Also in this case, the tilt amount, neutral axis, and twist of the measurement object T (steel pipe pile) at the position of each mounting unit 10 can be measured. In addition, for example, when a steel pipe pile is installed in water and is eroded from the outer peripheral side, by measuring the position of the neutral axis from the measurement surface t1 (inner peripheral surface), the decrease in the thickness of the steel pipe pile can be grasped. It is also possible to

Also, as shown in FIGS. 7A and 7B, a plurality of mounting units 10 may be attached to each of the three inner surfaces of the measuring object T, which is a box-shaped structure. In this case, each of the three inner surfaces becomes the measurement surface t1.
Further, although OFDR was used to measure the strain of each part of the optical fiber 15 in the above embodiment, other methods such as WDM (Wavelength Division Multiplexing) may be used.

(Fourth embodiment)
Next, a fourth embodiment according to the present invention will be described. This embodiment improves the mounting unit 10 described in the first embodiment and the like to make it easier to use. The same reference numerals are assigned to the same configurations as in the first embodiment, etc., and the description thereof will be omitted, and only the different points will be described. It should be noted that illustration of the optical fiber 15 and the like is omitted in FIG. 8A.

As shown in FIG. 8A, the mounting unit 30 of this embodiment includes a sheet member 31, main bars 32-34, and auxiliary bars 35 and . Main bars 32 to 34 and auxiliary bars 35 and 36 are fixed to sheet material 31 . Any fixing method may be used. For example, if the sheet material 31, the main rods 32 to 34, and the auxiliary rods 35 and 36 are made of metal (such as SUS), they may be fixed by welding. Moreover, you may fix with an adhesive agent etc. The mounting unit 30 is mounted on the measurement object T in the same manner as the mounting unit 10 and the like of the first embodiment. A method for fixing the mounting unit 30 to the measurement object T is arbitrary, but fixing by welding, an adhesive (for example, an epoxy adhesive), or the like can be adopted.

The surface of the sheet material 31 on the -X side is in contact with the surface t1 of the object T to be measured. A through hole 31 a is formed in the sheet material 31 . The through hole 31a is an elongated hole extending in the axial direction Z. As shown in FIG. Auxiliary bars 35 and 36 are arranged inside the through hole 31a. The auxiliary bars 35 and 36 are cylindrical and extend in the second direction Y. As shown in FIG. Since the diameters of the auxiliary rods 35 and 36 are larger than the thickness of the sheet material 31, part of the auxiliary rods 35 and 36 protrude from the through hole 31a toward the +X side. As an example, the sheet material 31 may have a thickness of 0.3 mm and the auxiliary bars 35 and 36 may have a diameter of 0.5 mm. The auxiliary bar 35 is positioned at the -Z side end of the through hole 31a, and the auxiliary bar 36 is positioned at the +Z side end of the through hole 31a.

The main bars 32 to 34 are fixed to the +X side surface of the sheet material 31 . The main rods 32-34 are cylindrical and extend in the second direction Y. As shown in FIG. The length of the main rods 32-34 is greater than the width of the through-hole 31a in the second direction Y. The main rods 32 to 34 are arranged so as to straddle the through hole 31a. The diameter of the main bars 32-34 is, for example, 1 mm.

As shown in FIG. 8B, the optical fiber 15 is connected to the +X side of the auxiliary bar 35, the -X side of the main bar 32, the +X side of the main bar 33, the -X side of the main bar 34, and the auxiliary bar. 36 are passing through the +X side in order. Since it passes through the -X side of the main rods 32 and 34, the optical fiber 15 is partially located inside the through hole 31a. By providing the through hole 31a in this manner, the protrusion of the mounting unit 30 from the surface t1 of the measurement object T can be reduced. Since the optical fiber 15 is passed through the +X side of the main rod 33, the through hole 31a may not be provided in the -X side of the main rod 33. FIG. In other words, two through holes 31a may be provided on the -X side of the main bar 32 and the -X side of the main bar 34, respectively. The optical fiber 15 is hardened with epoxy resin or the like and fixed to the sheet material 31 in a region on the −Z side of the main rod 32 and on the +Z side of the main rod 34 . In the section from the main rod 32 to the main rod 34, the optical fiber 15 is exposed without being hardened with epoxy resin or the like. A predetermined tension is applied to the optical fiber 15 in the section from the main rod 32 to the main rod 34, and the optical fiber 15 between the rods is linear. When the measurement object T is a pile material, in order to protect the exposed optical fiber 15 in the section from the main bar 32 to the main bar 34, it is preferable to cover at least the optical fiber 15 in this section with a protective tube or the like. . As a result, when the mounting unit 30 and the optical fiber 15 are press-fitted into the ground together with the pile material (object to be measured T), damage to the optical fiber 15 can be suppressed. The protective tube is, for example, semi-cylindrical and fixed to the object T to be measured.

In this embodiment, the section from the −Z side end of the sheet material 31 to the auxiliary bar 35 corresponds to the Z-axis measurement section Sz described in the first embodiment and the like. Also, the section from the main bar 32 to the main bar 33 corresponds to the X-axis measurement section Sx described in the first embodiment, etc., and the section from the main bar 33 to the main bar 34 corresponds to the third embodiment. It corresponds to the secondary X-axis measurement section Sx' described in the form.

The measurement method of this embodiment will be described below. In the following description, each symbol is defined as follows.
ε: strain generated in the optical fiber 15 Lch: distance between the neutral axis of the measurement object T before deformation and the measurement surface t1 La: length of the measurement section before deformation ∠θ'A0: influence of external force ∠(B'f0-A'f0-A'f1) angle ∠θ' Ai after deformation: ∠(B'f0-A'f0-A'f1) angle ∠θ' _Ai : Bending inclination L'a in the measurement section : Arc length R between point A0 and point Ai along measurement plane t1 after deformation: Bending radius caused by bending moment M acting on measurement object T

Consider a case where strain ε occurs in the optical fiber 15 due to the bending moment M acting on the measurement object T to cause bending deformation. R=Lch/ε and L′a=La×(1+ε). The radius of gyration caused by strain is R=Lch. Since L'a/(π×R)= _∠θ'Ai /π, the following equation (2) holds.
_∠θ′Ai =L′a/R=La/Lch×ε×(1+ε) (2)

Suppose that rust progresses on the measurement object T due to aging, Lch changes to L″ch, ε changes to ε″, and ∠θ′ _Ai changes to ∠θ″ _Ai : At this time, The following formula (3) is obtained based on the formula (2).
∠θ″ _Ai =L′a/R=La/L″ch×ε″×(1+ε″) (3)
By dividing the expression (2) by the expression (3), the following expression (4) is obtained.
_∠θ′Ai /∠θ″ _Ai =L″ch×ε″×(1+ε″)/Lch×ε×(1+ε) (4)
By transforming the formula (4), the following formula (5) is obtained.
L″ch/Lch= _∠θ′Ai /∠θ″ _Ai ×(ε×(1+ε))/(ε″×(1+ε″)) (5)

Since L″ch/Lch=1 when the rust has not progressed to the measurement object T, the following equation (6) is obtained from the equation (5).
_∠θ′Ai /∠θ″ _Ai =(ε″×(1+ε″)/(ε×(1+ε)) (6)
The strain ε of the measurement object T is empirically 100 to 500 με. Thus, the terms ε×ε and ε″×ε″ are sufficiently small to be ignored. Therefore, it can be approximated as (ε″×(1+ε″)/(ε×(1+ε))≈ε/ε″. Therefore, equation (7) is obtained by transforming equation (6).
∠θ″ _{Ai ≈∠θ′Ai} ×ε″/ε (7)
That is, ∠θ″ _Ai has a linear correlation with the strain ε, and also has a linear correlation with the bending moment M.

Next, strain ε occurs in the optical fiber 15 of length LB in the Z-axis measurement section Sz, resulting in length L′ _B . Consider the case of L'b. That is, L'B=LB*(1+ε) and L'b=Lb*(1+ε _B ). Suppose that _∠θA0 shown in FIG. 9 increases to _∠θ'A0 due to the bending moment M. ∠θ _A0 is obtained by the following formula (8) according to the included angle theorem for triangles.
∠θ _A0 = acos((D'i ^{^2} +LB ^{^2} -Lb ^{^2} )/(2×D'i×LB)) (9)
The tilt angle _∠θ'Ai generated at the point Ai by the bending moment M is obtained by the following equation (9).
_∠θ′Ai =( _∠θ′A0 − _∠θA0 )×2 (8)

Generally, it is known that the thickness of rust and the cross-sectional performance of steel are linearly correlated.
Strain ε changes to ε''', strain ε _B changes to ε _B ''', and ∠θ'Ai changes _to ∠θ''' _Ai think of. At this time, the following formula (9) is obtained based on the formula (5).
1>L″ _ch /Lch=∠θ′Ai/∠θ′″ _Ai ×(ε×(1+ε))/(ε′″×(1+ε′″)) (9)
_∠θ'Ai is calculated from the values (ε0, _εB0 ) of ε and _εB at the comparison reference time (point A0 in FIG. 10) when rust progresses, and ε''' after rust progresses, ∠θ''' _Ai is calculated from the value of ε''' _B . Let ∠θ' _Ai /∠θ''' _Ai = β. From FIG. 10, the rust progression thickness r is estimated.
The estimation formula is r=(1−β)/α (10).
α is the reduction gradient, which can be obtained by simulation as a theoretical coefficient from the standard dimensions of the steel material to be measured, and is published by the manufacturer for major steel materials such as steel sheet piles.

In FIG. 10, the straight line L1 indicates the case where it is assumed that the bending moment M (stress) is constant and rust progresses. A straight line L2 indicates a case where it is assumed that the bending moment M (stress) has increased without progressing rust. Assuming that the slope of the straight line L1 is β1, β1 can be obtained by simulation as a theoretical coefficient from the standard dimensions of the steel material to be measured, the rust progress r at the time of the comparison standard, and the strain value in the Sz section.

The values of εi and _εB i at the point Ai are obtained from the measurement results of the measuring device. A point As is a point located on the straight line L1 when the horizontal axis is εi. The value of the vertical axis at the point As is expressed as εAs. A point Am is a point located on the straight line L2 on the horizontal axis εi. The value of the vertical axis at point Am is represented as εAm. A value of ε _B i−εAm can be obtained from the graph.
The following formula (11) is a formula for estimating εAm from the measured value ε'i when it is assumed that rust has not progressed since the comparison reference time.
εAm=(εi−ε0)×α1+εB0 (11)

The following formula (12) is a formula for estimating εAs from the measured value ε'i when it is assumed that the external force has not changed since the comparison reference time. In other words, it is an equation for estimating the rust progress thickness r when it is assumed that the increase in ε' is due to the progress of rust.
εAs′=(εi−ε0)×β1+εB0 (12)
In equation (12), β1 can be obtained by simulation as a theoretical coefficient from the standard dimensions of the steel material to be measured, the rust progression r at the time of comparison, and the strain value in the Sz section, just like α1 in equation (11). can.

Due to the increase in external force, the point A0 (ε0, ε _B 0) at the time _of comparison changed to the point C1 (εCi, _εB Ci). Think about the case. When (εCi−ε0)/(εi−ε0)=η, the following equations (13) and (14) hold.
(ε _B i−εAm)=(β1−α1)×(εi−ε0)×η (13)
(εAs− _εB i)=(β1−α1)×(εi−ε0)×(1−η) (14)
The following equation (15) is obtained from equations (13) and (14).
η=(ε _B i−εAm)/(εAs−εAm) (15)

Using this η, the value of A'i (ε'i, _ε'B i) is calculated to obtain _∠θ'A0 . In addition, the ratio of ∠θ _A0 at the time of comparison reference to _∠θ'A0 after rust progresses ( _∠θA0 / _∠θ'A0 )=β is calculated, and the above-mentioned formula (10) is applied to obtain the rust progress thickness Estimate r. From the above, it is possible to obtain the progressed thickness of rust (the value of r) using the measurement result of the optical fiber 15 .

According to this embodiment, by pressing the pile material into the ground while the mounting unit 30 is attached to the pile material, the progress of rust in the underground pile material can be measured using light from the optical measuring device 20 through the optical fiber 15 . can be estimated by the measurement results of
Note that the measurement principle of this embodiment can also be applied to other measurement devices.

In addition, it is possible to appropriately replace the components in the above-described embodiments with well-known components without departing from the scope of the present invention, and the above-described embodiments and modifications may be combined as appropriate.
For example, in the measuring device 1 shown in FIG. 1B, another guide member (for example, the sixth guide member 19 in FIG. 4B) is arranged on the +Z side of the second guide member 14, and the -X side of the other guide member An optical fiber 15 may be passed through.

REFERENCE SIGNS LIST 1 measuring device 12 base member 13 first guide member 13a first arcuate surface 14 second guide member 14a second arcuate surface 15 optical fiber 20 optical measuring device T object to be measured t1 measurement surface

Claims (6)

one optical fiber in which the FBG is formed;
an optical measuring instrument connected to the optical fiber;
a first guide member having a first arcuate surface in contact with the optical fiber;
a second guide member having a second arcuate surface in contact with the optical fiber;
The first guide member and the second guide member are spaced apart in one direction and fixed to the measurement object,
The optical fiber has a first portion arranged along the measurement surface of the object to be measured and along the one direction, and a second portion having both ends in contact with the first arcuate surface and the second arcuate surface. , has
The second portion is arranged so as to move away from the measurement surface as it goes from the first arcuate surface to the second arcuate surface,
The optical measuring device is a measuring device that measures the strain amount of each part of the optical fiber by OFDR. Further comprising a base member to which the first guide member and the second guide member are fixed,
2. The measuring device according to claim 1, wherein said base member is fixed to said object to be measured. A measuring method using the measuring device according to claim 1,
The optical fiber is provided with a tension-applied section to which tension is applied and a non-tension section to which no tension is applied,
Measuring the strain amount of the optical fiber in the tension-free section by OFDR,
Perform temperature calibration using the measurement result of the strain amount of the optical fiber in the tension-free section,
Geometrically measuring the tilt amount of the measurement surface of the measurement object caused by the deformation of the measurement object using the measurement result of the strain amount of the optical fiber in the tension application section. , measurement method. A measuring method using the measuring device according to claim 1,
The optical fiber is provided with the first portion and the second portion arranged so as to be linearly separated from the measurement surface,
A result of OFDR measurement of the strain εz occurring in the first portion accompanying deformation of the measurement object, a result of OFDR measurement of the strain εx occurring in the second portion, and the neutral axis of the measurement object. measuring the distance L'ch of the neutral axis of the object to be measured from the measurement plane from the relational expression of R=L'ch÷εz based on the result of geometrically obtaining the radius of curvature R; Method. A measuring method using the measuring device according to claim 1,
The optical fiber is fixed to the object to be measured, and the amount of strain generated in the optical fiber due to the deformation of the object to be measured is measured by OFDR. A measurement method for geometrically measuring the amount and the amount of tilt in a second direction orthogonal to the first direction. calculating a combined tilt angle on a projection plane parallel to the first direction and the second direction based on the tilt amount in the first direction and the tilt amount in the second direction, and based on the amount of change in the combined tilt angle 6. The measurement method according to claim 5, wherein the torsion of the object to be measured about an axial direction perpendicular to both the first direction and the second direction is measured.

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